Problem Statement

Alex doesn't like boredom. That's why whenever he gets bored, he comes up with games. One long winter evening he came up with a game and decided to play it. Given a sequence consisting of n integers. The player can make several steps. In a single step he can choose an element of the sequence (let's denote it a_k) and delete it, at that all elements equal to a_k + 1 and a_k - 1 also must be deleted from the sequence. That step brings a_k points to the player. Alex is a perfectionist, so he decided to get as many points as possible. Help him. Input Array of integers representing array a. (1 <= n <= 10^5) (1 <= a_i <= 10^5). Output Print a single integer -- the maximum number of points that Alex can earn.